Method of covering the joint between wallboard and the resultant product



June 5, 1956 J. w. en l. ET AL METHOD OF COVERING THE JOINT BETWEEN WALLBOARD AND THE RESULTANT PRODUCT 4 Sheets-Sheet 1 Original Filed March 20. 1950 `lune 5, 1956 J, W. GILL ET AL 2,749,267

METHOD OF COVERING THE JOINT BETWEEN WALLBOARO AND THE RESULTANT PRODUCT Original Filed March 20, 1950 4 Sheets-Sheet 2 June 5, 1956 J. W. GILL ET AL METHGD 0F COVERING THE JOINT BETWEEN WALLBOARD AND THE; RESULTANT PRODUCT 4 Sheets-Sheet 3 Original Filed March 20, 1950 f (a zada/fw June 5, 1956 J. w. GILL ET AL 2,749,267

METHOD OF' COVERING THE JOINT BETWEEN WALLBOARD AND THE RESULTANT. PRODUCT Original Filed March 20, 1950 4 Sheets-Sheet 4 United States Patent O METHOD F COVERING THE JOINT BETWEEN WALLBOARD AND THE RESULTANT PRODUCT JosephW. Gill, Elmhurst, and Charles Russel Southwick,

Chicago, Ill., assignors to United States Gypsum Company, Chicago, Ill., a corporation of lliinois Continuation of application Serial No. 152,792, March 20, 1950. This application April 7, 1953, Serial No. 347,204

Claims. (Cl. 154-116) This invention relates to wallboard joint tape and has special reference to the use as aY joint tape for covering the joint between adjacent wallboards, of a strong strip of material having minute perforations that are relatively clean, with no burrs or tabs projecting outwardly from the "surfaces of the tape. Such perforations permit the escape of air entrapped beneath the strip, but will substantially prevent the escape therethrough of any adhesive employed to hold the strip in place over the joint.

More particularly, this invention relates to the use of spark perforated strips of suitable material as wallboard joint tape.

YThis application is a continuation of our copending application Serial No. 152,792, iiled March 30r 1950, now abandoned.

Tapes for covering wallboard joints have long been used. One of the most suitable of the prior art tapes is disclosed in the Page and Southwick Patent No. 2,180,433, dated November 2l, 1939. It is usually 2" to 4" wide and is preferably composed of strong vegetable or wood fiber paper in which a substantial portion of the fibers extend transversely to provide great lateral strength. The longitudinal edges are beveled or feathered to produce an invisible wallboard joint. The tape is also provided with perforations to permit the escape of air therethrough. Theperforations, which were formed by punches orvpins, had a minimum diameter of about ys and were often quite fuzzy about their edges with burrs and tabs not only in thefopenings, but extending outwardly from the edges thereof. Such holes also resulted in quite a substantial weakening of the tape.

In applying wallboard joint tape, the joint to be treated is rst covered with a suitable cement or other adhesive. The tape is placed overand pressed into this, and the air beneath escapes through the openings. With perforations of vabout 1A6" or more in diameter, the adhesive oozes therethrough, requiring that after drying it be removed and the outer surface of the tape be smoothed. Moreover, unless the tape is thereafter given a heavy coating of cement or other material, the hole pattern of the tape will show through the finish.

The tape of the present invention is far superior to that heretofore used. The perforations are formed by high potential sparks passing therethrough and are quite minute, being on the order of .005 in diameter, and generally inthe range of from .002" to .02" in diameter. Holes of this size permit the escape of any air entrapped beneath the vtape while substantially or entirely preventing any escape .therethrough of the wet cement or other adhesive. Consequently, with the spark perforated tape it is unnecessary to strike off portions of the adhesive or to smooth the exposed surfaces of the tape before applying the nish coats. In addition, there is substantially no likelihood ofthe hole pattern showing through the surface, even though only a thin coating of cement or paint is applied over the tape.

The spark formed perforations are relatively clean and free from burrs and tabs projecting from the surfaces of ice the tape,v such as result from the use of punches or pins, and do not materially decrease the strength of the tape.

An object of this invention is to provide a wallboard joint tape having openings of a size to permit the escape of-air while substantially preventing the passage -of any adhesive or cement therethrough.

Another object is to provide a perforated wallboard joint tape having openings that are relatively clean and .free from outwardly projecting burrs and tabs.

Still another object is to provide a wallboard joint including such tape.

A further object is to provide a perforated joint tape that substantially retains its strength after being perforated.

A still further object is to provide a machine to spark- Vperforate wallboard joint tape.

Another object is to provide such a perforating machine which will act automatically to perforate simultaneously a plurality of continuous strips of tape.

A further object is to provide a spark perforating machine having pairs of cooperating rotating electrode members between which the tape is fed for being perforated.

An additional object is to provide a perforating machine of the above type in which the periodicity of the high potential sparking source is so synchronized with the yelectrode members that maximum voltage occurs whenever pairsl of electrodes are adjacent each other in sparking position.

.Further vobjects and advantages will be apparent from the :following description and claims when considered with the "drawings, in which:

Fig..1'is an end elevational view of a spark perforating machine embodying the present invention, with the tape feeding mechanism omitted;

Fig. 2 is a cross-sectional View taken on the line 2-2 of Fig. l, and including tape feeding mechanism;

Fig. 3 is a top plan view of the machine shown in Fig. 1;

Fig. 4 is a side elevational view of an electrode member mounted on a shaft;

Fig. 5 is an end elevational view partially in cross section taken on the line 5-5 of Fig. 4;

Fig. 6 is a central, longitudinal, `cross-sectional view of an electrode member;

Fig. 7 is a modified form of spark perforating machine having two pairs of electrode shafts;

Fig. 8 is a wiring diagram of the spark perforating machine;

Fig. 9 is a plan view of a section of wallboard joint tape embodying the present invention; and

Fig. 10 is a transverse, cross-sectional View of the tape shown in Fig. 9 applied to a joint.

Referring more particularly to Figs. l-6 of the drawings, there is shown a machine for spark perforating wallboard joint tape. This machine comprises a base or table 11 which may be formed of angle-iron uprights 12 at each corner thereof with the two uprights on each side connected adjacent their upper ends by longitudinally extending channel irons 13. Joining the pairs of legs 12 at .each end of the table are angle irons 14 to which are also connected longitudinally extending, spaced angle irons 15. A top 16 secured on the channel irons 13 supports portions of the apparatus.

Fixed to the top 16 of the table are two spaced supporting members 17 and 18, each having a pair of vertically arranged bearing blocks 19 and 20 in which are journaled upper and lower electrode shafts 21 and 22. The electrode shafts .are formed of any suitable nonconducting material, such, for example as a phenol formaldehyde condensation product or other plastic. A plurality of electrode members 23 are mounted on the upper shaft 21 and an equal number of similar electrode members 24 3 are arranged on the lower electrode shaft 22 directly below those on the upper shaft 23.

Each of the electrode members, shown particularly in Figs. 4, 5 and 6, preferably comprises a bushing or hub 25, of bronze or other conducting material, for fitting on the electrode shafts 21 and 22. The hubs may be held on the shafts by means of set screws 26 threaded into tapped openings in the hubs. A plurality of electrode holders, such as chucks 27, are arranged equiangularly about the hub and also spaced longitudinally therealong. They preferably have their inner ends secured in openings provided therefor in the hub.

Electrodes 28 of any suitable material, such as a nickel, manganese, silicon alloy, are adjustably held in the chucks. Rod-shaped electrodes about 0.11 in diameter have proved satisfactory. However, any other electrodes capable of accomplishing the desired result may be employed.

The electrodes secured in the holders or chucks preferably extend radially with their outer ends lying in a helical path about the hub. As the electrodes are equiangularly spaced, the angle between adjacent ones, when five are employed, is 72. Although they may be spaced equally along the axis of the hub, they are preferably arranged with the three center chucks slightly closer together than are the two outer ones at each end of the hub. When the tape to be perforated is 25/16 in width, which is a cornmon width, the longitudinal spacing of the chucks may be about /m on centers.

The electrode members are arranged in pairs on the top and bottom shafts, so that each electrode on one cooperates with an electrode on the other, and as the shafts rotate in opposite directions, the pairs of upper and lower cooperating electrodes will be substantially aligned when their outer ends are adjacent each other. This spacing of the electrodes when they are in sparking position may be on the order of lg to 1A".

One pair of cooperating electrode members serves to perforate one tape with five holes arranged substantially transversely in each row. Any number of hubs may be arranged in spaced relation on the top and bottom shafts, so as to simultaneously perforate the desired number of tapes. In the machine illustrated in Fig. 1, seven such electrode members are mounted in spaced position on each shaft, for simultaneously perforating seven tapes fed between each cooperating pair.

At one end of each hub 25 a collector ring 29 is tixedly secured by any suitable means. Each of the collector rings 29 engages suitable brushes 30 or 31 mounted in upper and lower brush holders 30a and 31a respectively, arranged on suitable supports between the end members 17 and 18.

The electrode shafts 21 and 22 are preferably rotated in opposite directions at identical speeds by a synchronous motor 32 acting through suitable gearing 33, the directions of rotation being as shown by the arrows in Fig. 2. Thus during one rotation of the shafts each electrode of one electrode member will be aligned with a corresponding electrode of its cooperating electrode member.

Means are provided, such as the feed rolls 34 shown in Fig. 2, for feeding the strips or tapes through the machine between pairs of electrode members. An additional roll 35, or pair of rolls, may be provided at the entrance side of the machine for guiding the tape.

Transformers 36 of the type generally used for lighting neon tubes are preferably employed as the source of high potential for causing the sparking between adjacent electrodes. These transformers have a sufficiently high internal reactance to limit the current ow as soon as the spark commences and the external resistance drops to a relatively low value, while having a sufficiently high peak voltage to insure initiating a spark. The primary circuit of the transformer may be connected to an ordinary 11S-volt, 60-cycle A. C. source. The secondary circuit which includes the brushes engaging the collector rings 29 of a pair of electrode members, may produce fteen thousand volts across the electrodes with a current of sixty milliamperes. While such transformers have proved very satisfactory, others may be used and it is not essential that the transformers produce fifteen thousand volts in the secondary circuit, so long as the potential produced is sufficient to effect sparking through the tape. With the circuits above described, maximum voltage in the secondary will occur times a second, this being at the rate of 7,200 times a minute.

The synchronous motor 32 for driving the electrode shafts 21 and 22 is synchronized with the current phase in the transformer secondary circuit, so that the maximum voltage will occur whenever two electrodes of each pair of electrode members are adjacent each other in sparking position. With tive electrodes on each hub, the shafts will have to be rotated at 1440 R. P. M. in order to have the electrodes of a pair of electrode members aligned 7,200 times each minute. As the rotation of the shaft is synchronized with the voltage phase in the secondary circuit, the circuit will reach maximum voltage whenever a pair of electrodes are aligned and will result in a spark passing therebetween and through the tape being fed through the machine.

It has been found desirable to have the perforations average about 1A apart longitudinally ofthe tape. Such spacing will result when the tape is fed between the electrode members at a speed of 30 feet per minute. Increasing the speed of the tape will increase the spacing. Thus, at 35 feet a minute, the longitudinal distance between holes would be .29", and at 40 feet per minute the spacing would be .33.

If desired, the number of electrodes on each electrode member may be varied. For example, six electrodes could be employed to produce six holes in a line substantially transversely of the tape. However, in this case the electrode members would have to be driven at 1200 R. P. M. in order to maintain the time relationship between the sparking and the alignment of the wire eletrodes.

It has been found desirable to employ one transformer 36 for each pair of electrode members. However, the secondary circuits of the transformers may include more than a single pair of electrode members by suitably connecting overlapping pairs of such members on the upper and lower electrode shafts. In fact, a single transformer having the required characteristics could be used to effect the sparking between all seven pairs of electrode members.

Instead of having a single pair of electrode shafts with seven electrode members on each shaft, assuming that it is desired to operate upon seven tapes simultaneously, a construction having two pairs of shafts, such as shown in Fig. 7, may be employed. Accordingly, there would be two upper electrode shafts 21a and immediately below each shaft 21a a second or lower electrode shaft. The same electrode members 23 and 24 would be employed, the only difference being that with two pairs of shafts the spacing between adjacent electrode members is ncreased, thus reducing any liklihood of current flow from one electrode member to the adjacent members on the same shaft. A single synchronous motor 32 is employed for driving both pairs of electrode shafts through suitable gearing 33a.

A wiring diagram for the present apparatus is shown in Fig. 8. As may be seen thereon, energy is supplied to the motor 32 from a suitable 60-cycle A. C. 3-phase source 39, through switch 40 and conductors 41. Energy is supplied to the spark gap electrodes 28 from a source of energy 52 which may be an ordinary llO-volt, 60-cycle A. C. source, through transformers 36, by means of a circuit which may be traced as follows: From one side of source 52, through switch 51, time-delay switch 43, conductor 44, bus bar or trunk line 45, one of the conductors 45a, one of the resistors 47, one of conductors 46 to the arrasar primary of one of the transformers 36, and from the other side of the primary back through one of the conductors 48, bus bar or trunk line 49, conductor 50, and switch 51 to the other side of source 52. From the secondary of any one of the transformers 36, energy is supplied to any one of the spark gaps between electrodes 28 through conductors 53 and 54. Each of the transformers 36 has its primary winding connected to the bus bars 45 and 49 and each of the transformers has its secondary connected across one of the spark gaps.

The operating mechanism of the time-delay switch 43 is connected by means of conductors 42 and 42a across any two of the conductors 41.

Upon closing the switch 40 voltage is supplied from source 39 through conductors 41 to the motor 32 to operate the latter. At the same time voltage is supplied through conductors 42 to the operating mechanism of the time-delay switch 43 which then closes its contacts after the predetermined delay.

The variable resistors, such as the rheostats 47, serve a multiple purpose. By increasing the resistance in the primary circuits the current in the secondary circuits is decreased, resulting in a reduction in the size of the perforations formed. On the other hand, decreasing the resistance in the primary circuits serves to increase the size of the spark-produced perforations.

Another effect of increasing the resistance 47 in a primary circuit is to limit the flow of current in this circuit which occurs when sparking takes place between a pair of electrodes. In this Way the sparking potential of the transformers may be increased without overloading the transformers.

The tape 60 of the present invention is shown in Figs. 9 and 10. It is between 2 to 4" in width, one standard width being 25716. It is preferably composed of strong wood or vegetable ber paper in which a substantial portion of the fibers extends transversely, resulting in relatively great lateral strength. The longitudinal edges 61 are preferably feathered or beveled. As the tape 60 passes between a pair of electrode members 23 and 24 having five equiangularly spaced electrodes, live minute holes or perforations 62 will be formed per revolution of the electrode members in a more or less transverse line, which, however, angles slightly from one side of the tape to the other, due to the movement of the tape. Assuming conditions as above described, namely, electrode members such as shown in Figs. 4 and 5 rotating at 1440 R. P. M., with the tape traveling longitudinally at the rate of 30 feet per minute, the spacing between the holes in each longitudinal row will average about 1A, while the spacing between the ve perforations in each transverse row will depend upon the longitudinal spacing of the electrodes on the hubs.

The hole spacing and pattern in the tape are erratic. This results from the fact that the path of the sparks between pairs of electrodes varies considerably, due primarily to the lack of uniformity of the electrical resistance or conductivity of the. tape itself. Accordingly, in referring to the longitudinal spacing which, as above pointed out, varies in accordance with the speed of feed of the tape, the average spacing of the perforations in a longitudinal row is contemplated.

Fig. l0 discloses a joint embodying the present invention. It comprises the meeting edges of wallboards 63 attached to a stud or joist 64. The edges of the boards may be recessed on one side and the recess iilled with cement or other adhesive. The tape 60 is then positioned over, and secured in place by, the adhesive.

The perforations 62, resulting from the high potential spark passing between pairs of electrodes are minute, averaging about .005 in diameter, generally within the range of from .002" to .02 in diameter. Many of the openings are somewhat elongated or oval, and the diameters specified are the average diameters arrived at by averaging the minimum and maximum dimensions of the openings.

The surfaceedges of the perforations resulting from the high potential sparks are relatively smooth and are free from surface burrs and punched tabs which result when pins or punches are used to form the perforations. Moreover, a spark perforated tape as described herein loses very little strength due to the perforations.

When pins or punches are employed for perforating the tape, as has heretofore been the practice, the openings have been very much larger, ranging upwardly from a minimum of about and the edges of the holes are often burred and sometimes have tabs thereon. Moreover, the strength of the tape is materially reduced due to the perforations.

With holes ranging from a maximum of about .02 in diameter down to .002", air may escape through the openings, but the passage of cement and other adhesives there-V through is substantially prevented. Accordingly, when the tape is pressed into the cement or other adhesive, as is the practice in placing the tape over the wallboard joints, entrained air beneath the tape may escape but the adhesive will be prevented from passing through the openings.

The holes of perforations are preferably formed by sparking means. However, any other suitable means for producing holes of the desired type may be employed.

While particular embodiments of this invention have been illustrated and described, it will be understood of course that the invention is not to be limited thereto since many modications may be made, and it is contemplated therefore by the appended claims to cover any such modications as fall within the true spirit and scope of this invention.

We claim:

l. The combination with wallboards attached to a support and having edges in substantially abutting relationship forming a wallboard joint, of a strong thin cellulosic strip having perforations throughout with diameters from about 0.02 inch to 0.002 inch, said strip being adhesively secured over said joint and the edges of said wallboards adjacent thereto.

2. The method of covering the joint between adjacent wallboards which comprises adhesively securing over said joint a strong thin cellulosic strip provided with substantially uniformly arranged perforations having clean, smooth edges and diameters from about 0.02 inch to 0.002 inch to permit the escape of air entrapped beneath said strip during its application to said joint while substantially preventing the escape therethrough of adhesive employed to secure the strip in place.

3. The method of covering the joint between adjacent wallboards which comprises adhesively securing over said joint a strip of strong paper provided with spaced perforations throughout having clean, smooth edges and diameters from substantially 0.02 inch to substantially 0.002 inch to permit the escape of air entrapped beneath said strip during its application to said joint while substantially preventing the escape therethrough of adhesive employed to secure the strip in place.

4. The method of covering the joint between adjacent wallboards which comprises adhesively securing over said joint a strip of strong paper provided with spaced perforations throughout having diameters of substantially 0.005 inch to permit the escape of air entrapped beneath said strip during its application to said joint while substantially preventing the escape therethrough of adhesive employed to secure the strip in place.

5. The method of covering the joint between adjacent wallboards which comprises adhesively securing over said joint a strip of strong paper provided with substantially uniformly arranged spark-produced perforations having diameters from about 0.02 inch to 0.002 inch to permit the escape of air entrapped beneath said strip while substantially preventing the escape therethrough of adhesive employed to secure the strip in place.

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS Page July 21, 1936 8 Page et a1 Nov. 2l, 1939 Speer Mar. 23, 1943 Meaker Feb. 1, 1944 Raymond Apr. 12, 1949 Camp Jan. 9, 1951 Christman Feb. 2, 1954 

2. THE METHOD OF COVERING THE JOINT BETWEEN ADJACENT WALLBOARDS WHICH COMPRISES ADHESIVELY SECURING OVER SAID JOINT A STRONG THIN CELLULOSIC STRIP PROVIDED WITH SUBSTANTIALLY UNIFORMLY ARRANGED PERFORATIONS HAVING CLEAN, SMOOTH EDGES AND DIAMETERS FROM ABOUT 0.02 INCH TO 0.002 INCH TO PERMIT THE ESCAPE OF AIR ENTRAPPED BENEATH SAID STRIP DURING ITS APPLICATION TO SAID JOINT WHILE SUBSTANTIALLY PREVENTING THE ESCAPE THERETHROUGH OF ADHESIVE EMPOLYED TO SECURE THE STRIP IN PLACE. 